The defence minister, Marise Payne, has rejected Steve Ciobo’s suggestion it is a “decision for China” if it chooses to land bombers on disputed territory in the South China Sea.

Payne told Senate estimates the government was concerned about militarisation in the South China Sea, in direct contradiction of the trade minister’s refusal to engage in “megaphone diplomacy” on the issue.

On Friday in an interview with Sky News Ciobo failed to toe the government line set out by Payne and the foreign minister, Julie Bishop, following an incident in which a Chinese bomber capable of carrying a nuclear warhead had been on the disputed Paracel Islands.

Asked whether China should be landing bombers on disputed territory, Ciobo said: “That’s a decision for China. You might as well ask me should Russia do something with one of its submarines.

“I’m not going to get engaged in a commentary lecturing other countries about what they can and cannot do.

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“I’m not going to engage in megaphone diplomacy with China, to talk about whether they should or should not land a particular aircraft in disputed territory.”

At Senate estimates on Thursday, Labor’s Penny Wong asked if the comments reflected the Australian government’s position.

Frances Adamson, the secretary of the Department of Foreign Affairs and Trade, said the position was the one “set out by the minister for foreign affairs, the minister for defence, [and] the prime minister at various times”, adding it was “well known”.

Payne echoed the answer. Wong then asked if the Australian government’s position was that the issue was a decision for China.

“No, it means the government is concerned about the militarisation of those features,” Payne replied.

At the Coalition party room on Tuesday, Bishop said that “the relationship with China is a very important relationship and we must manage it for our mutual benefit but we need to uphold our principles”.

“That can lead to differences from time to time but those differences can be overstated,” she said.

Last week the Liberal chair of the parliamentary joint committee on intelligence and security, Andrew Hastie, used parliamentary privilege to allege the Australian Chinese billionaire Chau Chak Wing was the person funding the bribery of a senior United Nations official, the person identified in court documents as CC3.

Guardian Australia understands Labor intends to join a bipartisan report from the security committee on the espionage and foreign interference bill, one element of the package, to be finalised by Tuesday.

On Thursday the Labor leader, Bill Shorten, responded to a question about whether Labor would now support passage of the bill by promising the opposition would “keep working through the issues”.

“We put the national security of our nation above politics, but what we’ll also do is make sure that we get the detail right, and we’ll keep that process under way,” he told reporters in Canberra.

Labor has also faced scrutiny over its handling of China this week, after a Fairfax media report suggested questions put in Senate estimates by Senator Kimberley Kitching may have been written by the former Labor premier and senator Bob Carr, who now heads the Australia-China relations institute at the University of Technology Sydney.

Carr has denied he wrote the questions. On Tuesday Kitching distanced herself from Carr by saying she had never met him and clarifying she had not been in contact with him about the questions she asked about Malcolm Turnbull’s adviser John Garnaut.